JP5082369B2 - Polyester manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a polyester having a good electrostatic adhesion, a low foreign matter content, and a very high clarity.

  Polyesters typified by polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. are excellent in mechanical properties and chemical properties. Depending on the properties of each polyester, for example, Used in a wide range of fields such as textiles for clothing and industrial materials, films and sheets for packaging, magnetic tape, optics, bottles that are hollow molded products, casings for electrical and electronic components, and other engineering plastic molded products Has been. On the other hand, with the recent high-speed molding, for example, molding problems such as film breakage, fiber thread breakage, and generation of glazing have become apparent, and various products have higher precision, higher speed, and higher quality. With the demand for sensation, etc., the surface appearance of films, fibers, etc. is inferior, the image is disturbed as a video tape, the image is difficult to see due to light scattering as the surface layer of the liquid crystal screen, or the dielectric breakdown as a capacitor film Various problems have been pointed out. These problems are thought to be caused by the presence of polycondensation catalysts such as antimony compounds and various additives used in the resin production in the form of residues in the resin.

  For example, a polyester film is obtained by biaxially stretching after melt extrusion of polyester. That is, the sheet-like material melt-extruded by the extruder is brought into close contact with the surface of the rotating cooling drum and then taken, and then the sheet-like material is guided to a drawing roll disposed at the subsequent stage of the cooling drum, and longitudinally drawn. Furthermore, after transverse stretching with a tenter, it is heat-set (heat set). Here, in order to increase the uniformity of the thickness of the film and increase the casting speed, when the sheet-like material melt-extruded from the extrusion die is cooled on the surface of the rotary cooling drum, the sheet-like material and the drum surface And must be in close contact with sufficiently high adhesion. For this reason, as a method for increasing the adhesion between the sheet-like material and the surface of the rotating drum, a wire-like electrode is provided between the extrusion die and the cooling rotating drum, and a high voltage is applied to the unsolidified sheet. A so-called electrostatic contact casting method is often used in which static electricity is deposited on the surface of an object, and the sheet-like object is electrostatically attached to the surface of a cooling drum and rapidly cooled. That is, by electrostatically adhering the sheet material to the cooling drum, the sheet material adheres to the surface of the drum with high adhesion without forming a gap between the surface and the rotation speed of the cooling rotating drum. Even if the speed is increased, the sheet-like material is taken out without being displaced and uniformly cast, and a film having excellent thickness uniformity is efficiently manufactured.

  In the electrostatic adhesion casting method, it is effective to increase the amount of charge on the surface of the sheet-like material in order to improve the electrostatic adhesion of the sheet-like material to the cooling drum. It is known that it is effective to modify the polyester (hereinafter referred to as raw material polyester) to lower its specific resistance. As a method for reducing the specific resistance, an alkali metal or alkaline earth metal compound is added during the esterification or transesterification reaction in the production stage of the raw material polyester.

  On the other hand, even if the uniformity of the thickness of the polyester film is high, it cannot be said that the polyester film alone has sufficient quality, and the amount of foreign matter in the film is reduced to minimize defects such as fish eyes. There is a need. That is, clarity is required for the polyester film. Therefore, the raw material polyester also requires a high degree of clarity, and measures are taken to increase the clarity. As one of the methods, a method of increasing the clarity by generally filtering a polymer, which is a reaction product of polyester, using a fine filter is adopted. However, in recent years, higher clarity is required for polyester films used for optical films whose use is expanding.

For example, a polyester obtained by using an antimony compound as a polycondensation catalyst and adding a magnesium compound and a phosphorus compound, and having a high degree of clarity, a film polyester having a high degree of electrostatic adhesion and a small amount of foreign matter, and its polyester A manufacturing method is disclosed (see Patent Document 1).
JP 2002-327053 A

Further, in the polyester production method by the direct polycondensation method, a specific amount of at least one selected from a glycol-soluble magnesium compound, a manganese compound and a zinc compound, a phosphorus compound and a basic nitrogen compound is added from the outlet of the esterification reactor. In addition, a polyester for a film having a high clarity with a low electrostatic adhesion and a small amount of foreign matters added by the addition up to the initial polycondensation reactor inlet and a method for producing the same are disclosed (Patent Document 2). reference). Furthermore, in this patent document, it is preferable to add at least one selected from glycol-soluble magnesium compounds, manganese compounds, and zinc compounds and a phosphorus compound before the in-line mixer provided in the transfer line of the reactor. It is disclosed.
JP-A-3-292323

  In recent years, in the production method of polyester, not only the quality but also the production cost has been regarded as important. For example, in the case of a raw material polyester for optical polyester film that requires a high degree of clarity, continuous direct production that can reduce the production cost is possible. Production by the polycondensation method has been carried out. Generally, in the continuous polycondensation method, continuous production over a long period of 6 months or more is carried out. The above-mentioned conventionally known polyester production method can obtain a polyester with high clarity when production is started, but a magnesium compound or a magnesium compound and a phosphorus compound added for the purpose of imparting electrostatic adhesion over the course of operation The reaction product residue is deposited on the pipe wall and the can wall of the reactor, and the precipitate is dropped with the passage of operation time and mixed with the polyester, so that the clarity of the polyester is deteriorated with the passage of time. have.

  The present invention was made against the background of the problems of the prior art, has good electrostatic adhesion in the continuous polycondensation method, and has a small increase in the content of foreign matter even after long-term continuous operation. The present invention provides a production method capable of stably producing a polyester having a high degree of clarity.

In order to solve the above-mentioned problems, the present invention has finally been completed as a result of intensive studies. That is, the present invention is a method for producing a polyester comprising at least an alkaline earth metal compound and a phosphorus compound, and continuously supplies a slurry comprising dicarboxylic acid and glycol prepared in a slurry preparation tank to an esterification reaction tank, A polyester which is a continuous production method by performing an esterification reaction using one esterification reaction tank and subsequently performing polycondensation in a polycondensation reaction tank, wherein the polyester satisfies the following requirements simultaneously: It is a manufacturing method.
(1) The phosphorus compound is added to at least one location selected from the group consisting of a slurry preparation tank, an esterification reaction tank, a polycondensation reaction tank, and a transfer line between these tanks. (2) The alkaline earth metal Install a stirring-type inline mixer in at least one location selected from the group consisting of a slurry preparation tank, a transfer line from the slurry preparation tank to the esterification reaction tank, and a transfer line from the esterification reaction tank to the polycondensation reaction tank. And adding to the in-line mixer

  In this case, it is preferable that the place where the alkaline earth metal compound is added is an in-line mixer installed in a transfer line from the esterification reaction tank to the polycondensation reaction tank.

  In this case, the peripheral speed of the outer periphery of the stirring blade of the stirrer of the in-line mixer is preferably 2 to 100 m / second.

  In this case, it is preferable to add a part of the phosphorus compound described above to an in-line mixer to which the alkaline earth metal compound is added.

  Further, in this case, it is preferable to control the amount of heat per unit time of the reactant staying in the esterification reaction tank to be within ± 1.5% of the set value.

  Further, in this case, the amount of heat per unit time of the reactant staying in the esterification reaction tank is measured by measuring the temperature of the reactant, the slurry temperature and the slurry flow rate staying in the esterification reaction tank. It is preferable to control the amount of heat per unit time of the slurry supplied to the esterification reaction tank.

  In this case, the temperature and the liquid level of the reaction product staying in the esterification reaction tank are controlled so that they are within ± 3.0% and ± 0.2% of the set values, respectively. It is preferable to control the amount of heat per unit time of the slurry supplied to the chemical reaction tank to be within ± 2.0% of the set value.

  In this case, the temperature and the liquid level of the reaction product staying in the esterification reaction tank are controlled so that they are within ± 3.0% and ± 0.2% of the set values, respectively. Per unit time of the slurry supplied to the esterification reaction tank obtained from the temperature difference between the temperature of the reactant staying in the conversion reaction tank and the temperature of the slurry supplied to the esterification reaction tank, the slurry flow rate and the specific heat of the slurry It is preferable to control the amount of heat so that it is within ± 2.0% of the set value.

  In this case, the amount of alkaline earth metal in the residue on the filter after dissolving the obtained polyester in a solvent and filtering the solution through a membrane filter having an average pore size of 0.1 μm is 1 mg or less per kg of polyester. It is preferably maintained for at least 3 months from the start of production of the polyester.

In this case, the polyester obtained preferably has a melt specific resistance at 275 ° C. of 0.5 × 10 ⁸ Ω · cm or less.

  According to the polyester production method of the present invention, a polyester having a good electrostatic adhesion and having a very high degree of clarification can be stably produced over a long period of time with little increase in the content of foreign matter even after operation. . Therefore, the polyester obtained by the production method of the present invention suppresses molding problems such as breakage, yarn breakage, and generation of eyes when forming into a film or fiber. Moreover, since it has extremely high clarity, it can be suitably used as a raw material for optical films, hollow molded articles, ultrafine denier fibers and the like that are required to have few foreign matters and defects.

Hereinafter, the present invention will be described in detail.
The polyester referred to in the present invention refers to a polyester comprising a dicarboxylic acid and / or an ester-forming derivative thereof and a diol and / or an ester-forming derivative thereof.

  Dicarboxylic acids include succinic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1,3 -Cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, dimer acid, etc. Saturated aliphatic dicarboxylic acids exemplified, or ester-forming derivatives thereof, unsaturated aliphatic dicarboxylic acids exemplified by fumaric acid, maleic acid, itaconic acid, etc., or ester-forming derivatives thereof, orthophthalic acid, isophthalic acid, terephthalic acid Acid, 5 (Alkali metal) sulfoisophthalic acid, diphenic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid 4, 4'-biphenyl dicarboxylic acid, 4, 4'-biphenyl sulfone dicarboxylic acid, 4, 4'-biphenyl ether dicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p'-dicarboxylic acid, pamoic acid, anthracene dicarboxylic acid Examples thereof include aromatic dicarboxylic acids exemplified by acids and the like, and ester-forming derivatives thereof.

  Of these dicarboxylic acids, terephthalic acid and naphthalenedicarboxylic acid (especially 2,6-naphthalenedicarboxylic acid) are preferable from the viewpoint of the physical properties of the resulting polyester, and other dicarboxylic acids are used as constituents as necessary.

  In addition to these dicarboxylic acids, a polyvalent carboxylic acid may be used in combination if the amount is small. Examples of the polyvalent carboxylic acid include ethanetricarboxylic acid, propanetricarboxylic acid, butanetetracarboxylic acid, pyromellitic acid, trimellitic acid, trimesic acid, 3, 4, 3 ′, 4′-biphenyltetracarboxylic acid, and these Examples thereof include ester-forming derivatives.

  As glycols, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4 -Butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 1,10-decamethylene glycol, 1,12 dodecanediol, polyethylene glycol, polytrimethyl Aliphatic glycol, hydroquinone, 4,4′-dihydroxybisphenol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-bis (β-hydroxyethoxyphenyl) sulfone exemplified by tylene glycol and polytetramethylene glycol Bis (p-hydroxyphenyl) ether, bis (p-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) methane, 1,2-bis (p-hydroxyphenyl) ethane, bisphenol A, bisphenol C, 2,5- Examples include aromatic glycols exemplified by naphthalenediol, glycols obtained by adding ethylene oxide to these glycols, and the like.

  Of these glycols, ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,4-cyclohexanedimethanol are preferred.

  In addition to these glycols, polyhydric alcohols may be used in combination in small amounts. Examples of the polyhydric alcohol include trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, hexanetriol, and the like.

  Moreover, you may use together hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include lactic acid, citric acid, malic acid, tartaric acid, hydroxyacetic acid, 3-hydroxybutyric acid, p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid, 4-hydroxycyclohexanecarboxylic acid, or these And ester-forming derivatives thereof.

  Moreover, combined use of cyclic ester is also permitted. Examples of the cyclic ester include ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, and lactide.

  Examples of ester-forming derivatives of polyvalent carboxylic acids or hydroxycarboxylic acids include alkyl esters and hydroxylalkyl esters of these compounds.

  Examples of ester-forming derivatives of diols include esters of diols with lower aliphatic carboxylic acids such as acetic acid.

  As the polyester of the present invention, PET, PBT, polypropylene terephthalate, poly (1,4-cyclohexanedimethylene terephthalate), PEN, polybutylene naphthalate, polypropylene naphthalate and copolycondensates thereof are preferable, and among these, polyethylene terephthalate And this copolycondensate is particularly preferred. The copolycondensate is preferably composed of 50 mol% or more of ethylene terephthalate units, more preferably 70 mol% or more.

  The polycondensation catalyst used in the present invention is not limited. Conventionally known polycondensation catalysts such as antimony compounds, germanium compounds, titanium compounds, tin compounds and aluminum compounds can be used.

  Although it does not specifically limit as an antimony compound which can be used in this invention, An antimony trioxide, an antimony pentoxide, an antimony acetate, an antimony glycoloxide etc. are mentioned as a suitable compound, Especially use of antimony trioxide is preferable. Further, the germanium compound is not particularly limited, and examples thereof include germanium dioxide and germanium tetrachloride, and germanium dioxide is particularly preferable. As germanium dioxide, both crystalline and amorphous materials can be used.

  The titanium compound that can be used in the present invention is not particularly limited, but tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-tert-butyl titanate, tetracyclohexyl titanate, tetra Phenyl titanate, tetrabenzyl titanate, lithium oxalate titanate, potassium oxalate titanate, ammonium oxalate titanate, titanium oxide, composite oxide of titanium and silicon, zirconium, alkali metal, alkaline earth metal, etc., titanium orthoester or Condensed ortho ester, titanium ortho ester or reaction product of condensed ortho ester and hydroxycarboxylic acid, titanium ortho ester or condensed ortho ester and hydroxy carbonate A reaction product composed of an acid and a phosphorus compound, a titanium ortho ester or a condensed ortho ester and a polyhydric alcohol having at least two hydroxyl groups, a reaction product composed of a 2-hydroxycarboxylic acid and a base, etc. Of these, a composite oxide of titanium and silicon, a composite oxide of titanium and magnesium, a reaction product composed of titanium orthoester or condensed orthoester, hydroxycarboxylic acid and phosphorus compound is preferable.

  In addition, as tin compounds, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, triethyltin hydroxide, monobutylhydroxytin oxide, triisobutyltin acetate, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin sulfide, Examples thereof include dibutylhydroxytin oxide, methylstannoic acid, and ethylstannic acid, and the use of monobutylhydroxytin oxide is particularly preferable.

  Aluminum compounds include aluminum formate, aluminum acetate, aluminum propionate, aluminum oxalate, aluminum acrylate, aluminum laurate, aluminum stearate, aluminum benzoate, aluminum trichloroacetate, aluminum lactate, aluminum citrate, and aluminum tartrate. , Carboxylates such as aluminum salicylate, inorganic acid salts such as aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum phosphate, aluminum phosphonate, aluminum methoxide, aluminum ethoxide , Aluminum n-propoxide, Aluminum iso-propoxide, Aluminum n-butoxide Aluminum alkoxides such as aluminum t-butoxide, aluminum acetylacetonate, aluminum acetylacetate, aluminum ethylacetoacetate, aluminum chelate compounds such as aluminum ethylacetoacetate diiso-propoxide, organoaluminum compounds such as trimethylaluminum and triethylaluminum and these Partially hydrolyzed products of aluminum, reaction products consisting of aluminum alkoxides and aluminum chelate compounds and hydroxycarboxylic acids, aluminum oxide, ultrafine aluminum oxide, aluminum silicate, aluminum and titanium, silicon, zirconium, alkali metals, alkaline earth metals, etc. And complex oxides. Of these, carboxylates, inorganic acid salts and chelate compounds are preferred, and among these, aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride and aluminum acetylacetonate are particularly preferred.

  Among these aluminum compounds, aluminum acetate, aluminum chloride, aluminum hydroxide, and aluminum hydroxide chloride having a high aluminum content are preferable, and aluminum acetate, aluminum chloride, and aluminum hydroxide chloride are more preferable from the viewpoint of solubility. Furthermore, the use of aluminum acetate is particularly preferred from the viewpoint of not corroding the device.

Here, aluminum hydroxide chloride is a general term for what is generally called polyaluminum chloride or basic aluminum chloride, and those used for water supply can be used. These are represented by, for example, the general structural formula [Al ₂ (OH) _n Cl _6-n ] _m (where 1 ≦ n ≦ 5). Among these, those having a low chlorine content are preferable from the viewpoint of not corroding the device.

  The above-mentioned aluminum acetate is a general term for those having a structure of an aluminum salt of acetic acid represented by basic aluminum acetate, aluminum triacetate, aluminum acetate solution, etc. Among these, from the viewpoint of solubility and solution stability The use of basic aluminum acetate is preferred. Of the basic aluminum acetates, aluminum monoacetate, aluminum diacetate, or those stabilized with boric acid are preferred. When using the one stabilized with boric acid, it is preferable to use one stabilized with boric acid in an amount of equimolar or less with respect to basic aluminum acetate, and in particular, 1/2 to 1/3 molar amount. The use of basic aluminum acetate stabilized with boric acid is preferred. Examples of basic aluminum acetate stabilizers include urea and thiourea in addition to boric acid.

  In the present invention, the addition amount of the polycondensation catalyst is not limited. What is necessary is just to set suitably in the range which shows practical polycondensation catalyst activity. However, it is better to keep the addition to the minimum necessary from the viewpoint of suppressing the generation of foreign matter due to the polycondensation catalyst and ensuring the clarity of the resulting polyester.

  When using an antimony compound that is the most typical polycondensation catalyst, it is preferable to add an amount of antimony atoms with respect to the finally obtained polyester in an amount of 100 to 200 ppm. Conversely, if it exceeds 200 ppm, insoluble foreign matter is likely to be generated. A more preferable content of antimony atoms is 140 to 170 ppm.

  The alkaline earth metal compound used in the present invention is preferably at least one compound selected from Be, Mg, Ca, Sr, and Ba. The alkaline earth metal compound is added to lower the melt specific resistance of the polyester and improve electrostatic adhesion. In order to provide high electrostatic adhesion, it is preferable to use Mg or Ca compounds.

  In the present invention, it is preferable to further add an alkali metal compound. By adding the alkali metal compound, the effect of improving electrostatic adhesion can be increased, and a condensation reaction between glycol components, which is a side reaction, for example, when ethylene glycol is used as the glycol component, By-product is suppressed.

  The alkali metals used in the present invention are Li, Na, K, Rb, and Cs. The use of Na or K compounds is preferred.

  Examples of the alkaline earth metal and alkali metal compound include saturated aliphatic carboxylates such as formic acid, acetic acid, propionic acid, butyric acid and succinic acid, and unsaturated aliphatic carboxylic acids such as acrylic acid and methacrylic acid. Salts, aromatic carboxylates such as benzoic acid, halogen-containing carboxylates such as trichloroacetic acid, hydroxycarboxylates such as lactic acid, citric acid and salicylic acid, carbonic acid, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, hydrogen carbonate, Inorganic acid salts such as hydrogen phosphate, hydrogen sulfide, sulfurous acid, thiosulfuric acid, hydrochloric acid, hydrobromic acid, chloric acid and bromic acid, organic sulfonic acids such as 1-propanesulfonic acid, 1-pentanesulfonic acid and naphthalenesulfonic acid Salts, organic sulfates such as lauryl sulfate, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, tert Alkoxides such as butoxy, chelate compounds and the like acetylacetonate, hydrides, oxides, and hydroxides and the like. Of these compounds such as alkali metals and alkaline earth metals, when using strongly alkaline compounds such as hydroxides, these tend to be difficult to dissolve in diols such as ethylene glycol or organic solvents such as alcohols. It must be added to the polymerization system in an aqueous solution, which may cause a problem in the polymerization process. Furthermore, when a strongly alkaline material such as a hydroxide is used, the polyester is liable to undergo side reactions such as hydrolysis during the polymerization, and the polymerized polyester tends to be colored, and the hydrolysis resistance also decreases. Tend to. Accordingly, preferred alkali metal compounds or alkaline earth metal compounds of the present invention are alkali metal or alkaline earth metal saturated aliphatic carboxylates, unsaturated aliphatic carboxylates, aromatic carboxylates, halogen-containing compounds. Inorganic acid salt selected from carboxylate, hydroxycarboxylate, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, hydrogen phosphate, hydrogen sulfide, sulfurous acid, thiosulfuric acid, hydrochloric acid, hydrobromic acid, chloric acid, bromic acid, Organic sulfonates, organic sulfates, chelate compounds, and oxides. Among these, from the viewpoints of ease of handling and availability, it is preferable to use a saturated aliphatic carboxylate of metal such as alkaline earth metal or alkali metal, particularly acetate.

  The alkaline earth metal compound and the alkali metal compound are preferably added to the polyester production process as a glycol solution, particularly an ethylene glycol solution. These metal compounds may be added as a mixture of both, or may be added separately.

  The alkaline earth metal element content in the polyester is preferably 3 to 200 ppm. The alkaline earth metal element content in the polyester is more preferably 5 to 160 ppm, further preferably 10 to 120 ppm, and still more preferably 15 to 100 ppm. If the alkaline earth metal element content is less than 3 ppm, the decrease in the melt specific resistance of the polyester is reduced, and the electrostatic adhesion is deteriorated. On the other hand, when it exceeds 200 ppm, foreign matter generation due to the alkaline earth metal increases, stability such as thermal stability of the polyester decreases, and coloring of the polyester increases, which is not preferable.

  The alkali metal element content in the polyester is preferably 0.5 to 50 ppm. The alkali metal element content in the polyester is more preferably 1 to 40 ppm, further preferably 2 to 30 ppm, and further preferably 3 to 20 ppm. When the alkali metal element content is less than 0.5 ppm, the decrease in the melt specific resistance of the polyester is reduced and the electrostatic adhesion is deteriorated. Furthermore, the condensation reaction between glycol components, which are side reactions, increases. For example, when ethylene glycol is used as the glycol component, the by-product of diethylene glycol increases. The increase in the side reaction is not preferable because the lowering of the melting point of polyester and the deterioration of quality such as thermal oxidation stability are lowered. On the other hand, if it exceeds 50 ppm, the lowering of the specific resistance of the polyester and the effect of suppressing the condensation reaction between the glycol components reach a peak, and the coloring of the polyester increases and the color tone is lowered.

  In the present invention, it is preferable to add a phosphorus compound. Examples of the phosphorus compound include phosphoric acid, phosphorous acid, phosphonic acid and derivatives thereof. Specific examples include phosphoric acid, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, Dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, trimethyl phosphite, tributyl phosphite, methylphosphonic acid, dimethyl methylphosphonate, dimethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, phenylphosphone Acid diphenyl etc. are mentioned. Any of these may be used alone or in combination of two or more. Of these, trimethyl phosphate and / or phosphoric acid are preferred.

  The phosphorus compound preferably has an alkaline earth metal atom / phosphorus atom (atomic ratio) in the range of 1.0 to 10, particularly preferably 1.2 to 3.0. If the alkaline earth metal atom / phosphorus atom (atomic ratio) is less than 1.0, the effect of improving the electrostatic adhesion of the polyester is lowered, which is not preferable. On the other hand, when it exceeds 10, the heat resistance and resin color of the polyester deteriorate, which is not preferable. Here, the atomic ratio represents the ratio of the number of atoms, and the same applies when the atomic ratio is hereinafter described.

In the present invention, the polyester obtained by the above method preferably has a melt specific resistance at 275 ° C. of 0.5 × 10 ⁸ Ω · cm or less. 0.4 × 10 ⁸ Ω · cm or less is more preferable, and 0.3 × 10 ⁸ Ω · cm or less is more preferable. When the melt specific resistance of the polyester exceeds 0.5 × 10 ⁸ Ω · cm, the electrostatic adhesion is deteriorated, the casting speed is lowered, and the productivity is deteriorated. Here, the melt specific resistance correlates with the highest casting speed at which casting can be performed while suppressing the occurrence of pinnable in the electrostatic contact casting method, that is, electrostatic adhesion. A polymer having a lower melt resistivity can be cast at a higher speed, which is very important from the viewpoint of film productivity. However, if it is less than 0.1 × 10 ⁸ Ω · cm, the molded body using the polyester tends to form an electret, which is not preferable.

The melt specific resistance of the polyester was measured by measuring the current ( _io ) when a voltage of 120 V was applied by placing two electrodes (stainless steel wire) in the polyester melted at 275 ° C., and applying this to the following equation: Specific resistance value Si (Ω · m).
Si (Ω · m) = (A / L) × (V / _io )
[A: Area between electrodes (cm ² ), L = Distance between electrodes (cm), V = Voltage (V)]

In the present invention, it is preferable that the polyester obtained has a high clarity. The clarity of the polyester can also be evaluated by observing coarse particles (particles of 5 μm or more) contained in the polyester chip with a phase contrast microscope. That is, in this method, a polyester chip (one grain) is sandwiched between two cover glasses, melt-pressed at 280 ° C., rapidly cooled, and then observed in 20 fields of view with a 100 × phase contrast microscope. It can also be performed by a method of counting and evaluating the number of particles of 5 μm or more per 4 mm ² . If the total number of particles of 5 μm or more per 2.4 mm ² measured by this method is 30 or less, such polyester has few insoluble foreign matters (coarse particles), has a high degree of clarity, For example, since a film obtained by film formation has a high degree of clarity, it can be suitably used as an optical film that requires a high degree of clarity.

  The clarity of the polyester can be determined by determining the amount of metal in the residue on the filter after the polyester is dissolved in a solvent and the solution is filtered through a membrane filter having an average pore size of 0.1 μm. In the present invention, the insoluble alkaline earth metal content in the polyester is preferably 1 mg or less per 1 kg of the polyester. 0.8 mg or less is more preferable, and 0.6 mg or less is more preferable.

  Further, in the present invention, when the polyester is continuously produced over a long period of time, it is preferable that the above-mentioned clarity is maintained for at least 3 months from the start of the production of the polyester.

  Preferred embodiments for imparting the characteristics will be described later.

  In the polyester of the present invention, it is preferable to add a cobalt compound as a cobalt atom in an amount of less than 10 ppm with respect to the polyester for the purpose of improving the color tone. More preferably, it is 5 ppm or less, More preferably, it is 3 ppm or less. The cobalt compound is not particularly limited, and specific examples include cobalt acetate, cobalt nitrate, cobalt chloride, cobalt acetylacetonate, cobalt naphthenate, and hydrates thereof. Of these, cobalt acetate tetrahydrate is particularly preferred.

  In order to improve the color tone of the polyester of the present invention, it is also a preferred embodiment to use a color tone improving agent other than the cobalt compound. The color tone improving agent refers to a substance that changes color tone when added. The color tone improving agent of the present invention is not particularly limited, but inorganic and organic pigments, dyes, fluorescent whitening agents and the like are preferable.

  When a pigment or a dye is used, when the amount used is increased, there arises a problem that the brightness of the polycondensate decreases as a result. This causes the problem of being unacceptable for many applications. Therefore, the total amount of pigments and dyes used is preferably 20 ppm or less, more preferably 10 ppm or less, still more preferably 5 ppm or less, based on the polyester obtained. In such a region, the coloring can be effectively eliminated without reducing the brightness of the polycondensate.

  Further, it is preferable to use a fluorescent brightening agent alone or in combination with another color tone improving agent because the color tone is improved and, for example, the amount of the pigment or dye used may be small. As the fluorescent brightening agent, one commonly used one may be used, or two or more kinds may be used in combination. The amount added is preferably 50 ppm or less, more preferably 5 to 25 ppm, based on the polyester obtained.

  The inorganic pigment of the present invention is not particularly defined as long as it can change the color tone, for example, titanium dioxide, carbon black, iron black, nickel titanium yellow, yellow iron oxide, cadmium yellow, chrome lead, chrome titanium yellow, Examples include zinc ferrite pigments, dials, cadmium red, molybdenum red, chromium oxide, spinel green, chrome orange, cadmium orange, ultramarine blue, bitumen, and cobalt blue. Of these, chromium oxide, ultramarine blue, bitumen, and cobalt blue are preferable, and ultramarine blue and cobalt blue are more preferable. One or more of these inorganic pigments may be used in combination as necessary.

  The organic pigments and dyes of the present invention are not specified as long as they can change the color tone, but, for example, Pigment Red 5, 22, 23, 31, 38, 48: 1, 48: 2 displayed by a color index. , 48: 3, 48: 4, 52, 53: 1, 57: 1, 122, 123, 144, 146, 151, 166, 170, 177, 178, 179, 187, 202, 207, 209, 213, 214 , 220, 221, 247, 254, 255, 263, 272, Pigment Orange 13, 16, 31, 36, 43, 61, 64, 71, Pigment Brown 23, Pigment Yellow 1, 3, 12, 13, 14, 17 , 55, 73 , 74, 81, 83, 93, 94, 95, 97, 109, 110, 128, 130, 133, 136, 138, 147, 150, 151, 154, 180, 181, 183, 190, 191, 191: 1 , 199, Pigment Green 7, 36, Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15.4, 15: 6, 29, 60, 64, 68, Pigment Violet 19, 23, 37, 44, Solvent Red 52, 117, 135, 169, 176, Disperse Red 5, Solvent Orange 63, 67, 68, 72, 78, Solvent Yellow 98, 103, 105, 113, 116, Di perseYellow 54, 64, 160, Solvent Green 3, 20, 26, Solvent Blue 35, 45, 78, 90, 94, 95, 104, 122, 132, Solvent Violet 31, and the like. Other anthraquinone, phthalocyanine, quinacridone, isoindolinone, dioxazine, quinophthalone, perylene, perinone, benzimidazolone, diarylide, bat, indigo, quinophthalone, diketopyrrolo Examples include pyrrole and anthrapyrrolidone dyes / pigments.

  Of these, Pigment Red 187, 263, Pigment Blue 15: 1, 15: 3, 29, 60, Pigment Violet 19, Solvent Red 135, Solvent Blue 45, 90, 104, 122, and anthraquinone and phthalocyanine dyes / Pigments are preferred. Furthermore, anthraquinone and phthalocyanine dyes / pigments are particularly preferred.

  The selected pigments and / or dyes preferably satisfy the following conditions. First, the pigments and dyes must be non-extractable from the polycondensate for maximum safety. It is stable to sunlight and a wide range of temperature and humidity conditions. Furthermore, it does not cause sublimation or hue changes as a result of the extremely high temperatures encountered during the production of polyester. Furthermore, it is preferable that these pigments and dyes do not adversely affect the physical properties of the polyester polymer.

  A pigment and / or a dye satisfying these conditions is not particularly limited as long as it improves the color tone of the polyester. For example, in Japanese Translation of PCT International Publication No. 2000-511111, a certain blue 1,4-bis (2,6-dialkylanilino) is used. ) Color tone improvers that mainly use anthraquinone and combine red anthraquinone and anthrapyridone (3H-dibenzo [fi, j] isoquinoline-2,7-dione) compounds according to the hue are exemplified. be able to. These dyes have suitable color characteristics, are stable to heat, light, humidity and various environmental factors and can be included in the polyester polymer structure during polycondensation, and are known organic dyes. Overcome many of the problems you encounter. It is stable to UV light, high temperature and hydrolysis. Furthermore, the amount of the blue component and the red component can be changed as necessary so as to work effectively for polyesters having different degrees of coloring.

  As the optical brightener of the present invention, those generally used may be used alone or in combination. For example, benzoxazoline-based fluorescent whitening agents, preferably UVITEX OB, UVITEX OB-P, UVITEX OB-ONE, CHIARI Specialty Chemicals, Ltd., HOTALUX KS, manufactured by Clariant, and those described in JP-A-10-1563 Can be preferably used.

  Since the above-described color tone improving agent achieves an achromatic hue, it can be used in any combination of types and addition ratios. Further, the color tone improving agent may be added at any stage of the polycondensation, after the polycondensation reaction, or at any stage from the end of the polycondensation reaction to the time of molding. . Further, the addition method is preferably added after dissolving in powder or one of polyester monomers during polycondensation. Furthermore, after completion of the polycondensation reaction, it is preferably added as a powder or a master batch.

  Moreover, when a problem arises in the dispersibility of pigments or the like, it may be preferable to use a dispersant as necessary. The dispersant is not particularly defined as long as it aids in dispersing the pigment. For example, N, N′-ethylenebismyristic acid amide, N, N′-ethylenebisstearic acid amide, N, N′-ethylenebisoleic acid N, N′-methylenebismyristic acid amide, N, N′-methylenebisstearic acid amide, N, N′-methylenebisoleic acid amide, and other N, N′-alkylenebisfatty acid amides. Of these, N, N'-methylenebisstearic acid amide is preferable. The amount added depends on the performance, but it is 10 to 200% by mass, preferably 40 to 150% by mass, based on the pigment.

  The polyester of the present invention preferably has an intrinsic viscosity of 0.580 to 0.630 dl / g. Polyester having an intrinsic viscosity of less than 0.580 dl / g is not preferable because the mechanical properties of a molded article such as a film obtained by film formation are deteriorated, and conversely, it exceeds 0.630 dl / g. Such a polyester is not preferred because the load on the extruder when the polyester chip produced after the polycondensation reaction is extruded into a sheet increases and the productivity decreases. A more preferable intrinsic viscosity is 0.600 to 0.620 dl / g.

  In the present invention, it is preferable to carry out the polyester by a direct esterification method and a continuous method.

  The direct esterification method is advantageous in terms of economy as compared with the transesterification method. The continuous polycondensation method is advantageous in terms of quality uniformity and economy as compared to the batch polycondensation method.

  In the present invention, the reaction vessel size in the esterification and polycondensation steps, the production conditions in each step, and the like can be appropriately selected without limitation.

  For example, a slurry containing 1.2 to 2.5 moles, preferably 1.3 to 2.2 moles of ethylene glycol with respect to 1 mole of terephthalic acid is prepared and used in the esterification reaction step. Supply continuously. The esterification reaction is preferably carried out using one esterification reaction tank while removing water produced by the reaction from the system with a rectification column. The temperature of the esterification reaction is 240 to 270 ° C., preferably 245 to 265 ° C., the pressure is preferably normal pressure to 300 KPa, more preferably 20 to 280 kPa, and further preferably 40 to 260 kPa. Subsequently, it is transferred to a polycondensation reaction tank to carry out polycondensation. The number of reaction tanks in the polycondensation step is not limited. In general, a three-stage system of initial polycondensation, middle-stage polycondensation, and late-stage polycondensation is taken, but a one-stage or two-stage system is preferred in view of cost reduction. Regarding the polycondensation reaction conditions, for example, the reaction temperature of the first stage polycondensation in a two-stage system is 250 to 290 ° C., preferably 260 to 280 ° C., and the pressure is 10 to 2.7 KPa, preferably 2.7. The temperature of the second stage polycondensation reaction is 265 to 300 ° C, preferably 275 to 295 ° C, and the pressure is 1.3 to 0.13 KPa, preferably 0.65 to 0.065 KPa. is there.

In the present invention, (1) the phosphorus compound is added to at least one point selected from the group consisting of a slurry preparation tank, an esterification reaction tank, a polycondensation reaction tank, and a transfer line between these tanks (2) At least one place selected from the group consisting of a slurry preparation tank, a transfer line from the slurry preparation tank to the esterification reaction tank, and a transfer line from the esterification reaction tank to the polycondensation reaction tank, the alkaline earth metal compound is stirred. It is preferable that the in-line mixer is installed and added to the in-line mixer at the same time. By this measure, it is possible to stably produce a polyester having a good electrostatic adhesion and having a very high degree of clarity with little increase in foreign matter content even after long-term continuous operation.
In addition, as a method of installing an in-line mixer in a slurry preparation tank, the method of providing a circulation line in a slurry preparation tank and installing an in-line mixer in this circulation line can be mentioned. Thereby, an alkaline-earth metal compound can be added to a slurry preparation tank via an in-line mixer.

  The peripheral speed of the outer periphery of the stirring blade of the in-line mixer is preferably 2 to 100 m / sec. 4-90 m / sec is more preferable and 6-80 m / sec is further more preferable. By using a stirring type in-line mixer having such characteristics, an effect that cannot be achieved by the addition of a static mixer, which is a publicly-known technique, can be achieved.

  The in-line mixer used in the present invention is not limited in its structure and size as long as it satisfies the above requirements and can express a uniform mixing effect. For example, the in-line mixer for the purpose of dispersing and mixing the slurry disclosed in JP-A-8-299771 An inline mixer is preferred.

  The installation place of the in-line mixer may be any of those described above, but it is preferable to use a transfer line from the ester reaction tank to the first polycondensation reaction tank. By the correspondence, the effect of the present invention can be manifested more remarkably.

  By carrying out by the above method, the production of foreign matter due to the alkaline earth metal compound is suppressed, a clearer polyester is obtained over a long period of time, and the above-mentioned degree of clarity can be stably maintained over a long period of time. That is, a conventionally known polyester production method can obtain a polyester with high clarity when production is started, but an alkaline earth metal compound such as a magnesium compound added for the purpose of imparting electrostatic adhesion over the course of operation. Alternatively, the alkaline earth metal compound, the phosphorus compound, and the reaction product of these and the polyester oligomer are deposited on the pipe or the can wall of the reactor, and the precipitate drops off with the passage of operation time and is mixed into the polyester. The polyester has a problem that the clarity of the polyester deteriorates with time. The present invention has been achieved by adding an alkaline earth metal compound to a stirring-type in-line mixer to suppress the formation of precipitates that are deposited on the pipe or the can wall of the reactor by improving the stirring ability. .

  In the present invention, it is preferable to add at least a part of the above-described phosphorus compound to an in-line mixer to which the alkaline earth metal compound is added. The implementation of this method is preferred because it suppresses the formation of precipitates deposited on the above-mentioned alkaline earth metal compound piping and reactor can walls, and electrostatic adhesion is further improved.

  The addition method in the case of implementing by the said method is not limited. It may be added from an addition port separate from the alkaline earth metal compound, or may be added from the same addition port by mixing them together in advance or in an addition line.

  In the present invention, the transfer line between the reaction tanks in the above production process is branched into a plurality of lines, and the agitated inline mixer described above is installed in each branched line, and at least one of the branched lines is used. The polyester intermediate is transported, and the above-mentioned alkaline earth metal compound is added to an in-line mixer installed in the line through which the polyester intermediate flows, and the clarity of the polyester obtained by continuous operation over a long period of time deteriorates. It is more preferable to continue the continuous production by switching the flow path of the polyester intermediate, changing the flow path to the in-line mixer installed in the flow path where the addition of the alkaline earth metal compound is switched at the same time. This is an embodiment.

  That is, when the amount of magnesium in the residue on the filter after dissolving the polyester obtained by the above method in a solvent and filtering the solution through a membrane filter having an average pore size of 0.1 μm exceeds 1 mg per kg of the polyester, It is preferable to continue the continuous production by switching the path and changing to the in-line mixer installed in the flow path where the addition of the alkaline earth metal compound is switched simultaneously with the switching of the flow path.

  Furthermore, it is a preferred embodiment to perform washing of the in-line mixer to which the alkaline earth metal compound has been added before switching after switching the flow path by the above method.

  According to the above aspect, in the production after the flow path switching, when the flow path needs to be switched, the flow path of the washed inline mixer can be used. As a result, the number of branch lines is set to two. This is a preferred embodiment because the clarification of the polyester can be stably produced over a long period of time by alternating use.

  The cleaning method is not limited, but for example, a method of circulating triethylene glycol heated to 250 to 270 ° C. from the inlet of the in-line mixer to the outlet and continuously circulating for a predetermined time while venting gas from the top of the mixer. Can be mentioned.

  After washing by the above method, the in-line mixer may be disassembled and perfect cleaning may be performed by buffing or the like for each component such as a stirrer.

  In the present invention described above, by adding the alkaline earth metal compound to the stirring-type in-line mixer, the generation of foreign matter due to the alkaline earth metal compound is suppressed, and a clearer polyester is obtained over a long period of time. Can be maintained for a long time. That is, a conventionally known polyester production method can obtain a polyester with high clarity when production is started, but an alkaline earth metal compound such as a magnesium compound added for the purpose of imparting electrostatic adhesion over the course of operation. Alternatively, the alkaline earth metal compound, the phosphorus compound, and the reaction product of these and the polyester oligomer are deposited on the pipe or the can wall of the reactor, and the precipitate drops off with the passage of operation time and is mixed into the polyester. The polyester has a problem that the clarity of the polyester deteriorates with time. The present invention has been achieved by adding an alkaline earth metal compound to a stirring-type in-line mixer to suppress the formation of precipitates that are deposited on the pipe or the can wall of the reactor by improving the stirring ability. . Further, in the present invention, in the improved production method, since the alkaline earth metal compound is added to the in-line mixer stirred at a high speed, the generation of the precipitate deposited on the can wall is greatly reduced. Although the period during which a high-clarity polyester is obtained is extended, the formation of the precipitate cannot be completely suppressed, so that the clarity may be deteriorated. Accordingly, the clarity of the polyester is evaluated, and when the clarity is deteriorated as described above, the addition line of the alkaline earth metal compound is switched to allow further extension of the period and stabilization of the quality.

  The evaluation frequency of the clarity of the polyester in the present invention is not limited. Daily evaluation is most preferred. Among the methods for evaluating the degree of clarity of the polyester, the method for evaluating the number of coarse particles contained in the polyester chip is simpler than the method for evaluating the amount of insoluble matter, so the frequency of evaluation by the method for evaluating the number of coarse particles is increased. In a preferred embodiment, the addition line switching is determined by increasing the measurement frequency of the insoluble content evaluation method when the evaluation result tends to deteriorate. For example, in a steady state, the coarse particle number evaluation method is measured once / day, the insoluble content amount evaluation method is measured once / week, and when the increase in the number of coarse particles is observed, the measurement frequency is increased. Is preferred. What is necessary is just to set this measurement frequency suitably according to the use use and required quality of polyester to produce.

  In the present invention, the conditions for the esterification reaction and the polycondensation reaction are not limited, but the fluctuation of the esterification reaction greatly affects the quality fluctuation of the final polyester. In particular, in the method for producing a polyester in one esterification reaction vessel of the present invention, since the fluctuation of the esterification reaction is larger than that in a polyester production method provided with a plurality of esterification reaction vessels, the following method is used. Is a preferred embodiment.

  It is important to control the amount of heat per unit time of the reactant staying in the esterification reaction tank so that it is within ± 1.5% of the set value. The fluctuation range of the amount of heat per unit time of the reaction product staying in the esterification reaction tank is more preferably within ± 1.3%, and further preferably within ± 1.1%. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance. When the above fluctuation range exceeds ± 1.5%, the variation of the carboxyl end group concentration of the polyester oligomer at the outlet of the esterification reaction tank becomes large, and as a result, the quality variation such as the carboxyl end group concentration and color tone of the final polyester changes. Since it becomes large, it is not preferable. In addition, depending on the type of polycondensation catalyst used, the polycondensation catalyst activity may vary, and the quality variation of the polyester may be further increased.

  The method for controlling the amount of heat per unit time of the reactant staying in the esterification reaction tank is not limited. For example, the following methods are mentioned.

  The first method measures the temperature and flow rate of the reactants retained in the esterification reaction tank, the slurry temperature and the flow rate, so that the amount of heat per unit time of the reactants retained in the esterification reaction tank is constant. It is preferable to carry out by controlling the amount of heat per unit time brought into the slurry. In this method, as a method of controlling the amount of heat per unit time brought into the slurry, there is a method of controlling the slurry temperature, the slurry supply amount, and both, but if the slurry supply amount is changed, the liquid level fluctuation of the esterification reaction tank etc. Since this causes fluctuations in factors affecting the esterification reaction, it is preferable to control the slurry temperature so that the slurry flow rate is constant. In the case of carrying out by this method, it is preferable to control the slurry supply amount within a set value ± 3%. Within ± 2.5% is more preferred, and within ± 2.0% is even more preferred. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance. The method for controlling the supply amount of the slurry is not limited. For example, a method of changing the feed pump rotation speed so as to achieve a set flow rate using a flow meter, a bypass line returning to the slurry preparation tank is provided after the feed pump of the feed line, and the revolution speed of the feed pump is set. A method of adjusting the opening of the control valve provided in the bypass line so that the flow rate of the flow meter provided in the liquid feed line is constant, and providing a difference in height between the slurry preparation tank and the esterification reaction tank. Then, the slurry is fed by the head pressure, and adjustment is performed by adjusting the opening of the control valve provided in the liquid feeding line so that the flow rate of the flow meter provided in the liquid feeding line becomes constant. The type of flow meter is not limited. For example, a rotor flow meter, a rotor piston flow meter, an oval flow meter, a micro motion flow meter, and the like can be given. Moreover, you may adjust so that the liquid level of an esterification reaction tank may become fixed. Moreover, it is preferable to measure the temperature inside the reaction tank of 200 to 400 mm from the can wall at the bottom of the reaction tank.

  The amount of reactant passing through the esterification reactor is measured by measuring the reactant flow rate at the outlet of the esterification reactor using a high-temperature flow meter, or the amount of slurry supplied to the esterification reactor The method etc. which are computed from the liquid level of an esterification reaction tank are mentioned.

  In the second method, the temperature and the liquid level of the reaction product staying in the esterification reaction tank are controlled to be within ± 3.0% and ± 0.2% of the set values, respectively, In this method, the amount of heat per unit time of the slurry supplied to the chemical reaction tank is controlled to be within ± 1.5% of the set value.

  The variation in the carboxyl end group concentration of the polyester oligomer at the outlet of the esterification reactor is affected by the temperature of the esterification tank and the residence time (in the limited polyester production line, the liquid level of the reactor). It is preferable to control within the above range. For example, the temperature is more preferably within a set value ± 2.0%. On the other hand, the lower limit is most preferably ± 0% with no variation, but from the viewpoint of cost performance, ± 0.2% is preferable, and ± 0.5% is more preferable. The liquid level is preferably within a set value ± 0.2%, and more preferably within ± 0.1%. On the other hand, the lower limit is most preferably ± 0%, which is unchanged, but from the viewpoint of cost performance, ± 0.02% is preferable, and ± 0.05% is more preferable. The liquid level can be controlled by setting the slurry flow rate control within the above range.

  It is preferable to control the amount of heat per unit time of the slurry supplied to the esterification reaction tank to be within ± 1.5% of the set value after satisfying the above requirements. Within ± 1.3% is more preferred, and within ± 1.1% is even more preferred. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance.

  In the third method, as in the second method, the temperature and the liquid level of the reactant staying in the esterification reaction tank are within ± 3.0% and ± 0.2% of the set values, respectively. Then, the temperature difference between the temperature of the reactant staying in the esterification reaction tank and the slurry temperature supplied to the esterification reaction tank, the slurry flow rate, and the specific heat of the slurry are obtained and supplied to the esterification reaction tank. It is preferable to control the amount of heat per unit time of the slurry to be within ± 1.5% of the set value. The variation range of the amount of heat per unit time of the slurry supplied into the esterification reaction tank determined by the above method is more preferably within ± 1.3%, and even more preferably within ± 1.1%. The lower limit is most preferably ± 0%, which is unchanged, but is preferably ± 0.1%, more preferably ± 0.3% from the viewpoint of cost performance.

  In this method, the calorie fluctuation per unit time of the reactant staying in the esterification reaction tank can be approximated by the temperature of the reactant staying in the esterification reaction tank, and the fluctuation of the calorific value is in the esterification reaction tank. The temperature difference between the temperature of the reactant staying in the slurry and the slurry temperature supplied to the esterification reactor, the slurry flow rate and the specific heat of the slurry are obtained, and the fluctuation of the calorie per unit time of the slurry supplied to the esterification reactor is reduced. This is based on the finding that it can be suppressed. That is, if the variation in the amount of heat brought in by the slurry supplied to the esterification reaction tank is suppressed, the variation in the amount of heat per unit time of the reactant staying in the esterification reaction tank can be suppressed, and the supply to the esterification reaction tank When the fluctuation of the amount of heat brought in by the slurry is increased, an over-response of the temperature control of the esterification reaction tank may occur, and it may be difficult to control the temperature of the reactants staying in the esterification reaction tank. This method leads to avoidance of the overresponse, suppresses fluctuations in the esterification reaction in the esterification reaction tank, and suppresses fluctuations in the carboxyl end group concentration of the polyester oligomer at the outlet of the esterification reaction tank.

  The method for controlling the amount of heat per unit time of the slurry supplied into the esterification reaction tank in the above method is not limited. For example, there is a method of measuring the temperature and slurry flow rate of the slurry supplied into the esterification reaction tank and controlling the slurry temperature and / or slurry flow rate. The method of controlling the slurry flow rate is a reaction in the esterification reaction tank. Since this leads to fluctuations in factors affecting the esterification reaction such as fluctuations in the liquid level of the material, it is preferable to control the slurry temperature so that the slurry flow rate is constant. In the case of carrying out by this method, it is preferable to control the slurry supply amount within a set value ± 3.0%. Within ± 2.5% is more preferred, and within ± 2.0% is even more preferred. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance. The method for controlling the supply amount of the slurry is not limited. For example, a method of changing the feed pump rotation speed so as to achieve a set flow rate using a flow meter, a bypass line returning to the slurry preparation tank is provided after the feed pump of the feed line, and the revolution speed of the feed pump is set. A method of adjusting the opening of the control valve provided in the bypass line so that the flow rate of the flow meter provided in the liquid feed line is constant, and providing a difference in height between the slurry preparation tank and the esterification reaction tank. Then, the slurry is fed by the head pressure, and adjustment is performed by adjusting the opening of the control valve provided in the liquid feeding line so that the flow rate of the flow meter provided in the liquid feeding line becomes constant. The type of flow meter is not limited. For example, a rotor flow meter, a rotor piston flow meter, an oval flow meter, a micro motion flow meter, and the like can be given. Moreover, you may adjust so that the liquid level of an esterification reaction tank may become fixed.

  Moreover, the control method of the slurry temperature in the case of implementing with the said method is not limited. For example, it is preferable to detect and control the temperature of the slurry preparation tank and / or the terephthalic acid temperature and feed back to the glycol temperature supplied to the preparation tank. The slurry temperature control may be controlled by installing a heat exchanger in the slurry preparation tank or slurry transfer line. In addition, a circulation line may be provided in the slurry preparation tank to circulate the slurry in the slurry preparation tank to improve the accuracy of temperature control. In the case of this method, it is preferable to add a temperature control function also to the circulation line. The above methods may be performed alone or a plurality of methods may be combined. Further, a slurry storage tank may be provided between the slurry preparation tank outlet and the esterification reaction tank supply to improve the accuracy of the slurry temperature control. In the case of this method, a temperature control mechanism may be added to the slurry storage tank. As a method of providing the slurry storage tank, the slurry adjustment in the slurry preparation tank may be carried out by a batch method. The batch type slurry preparation method facilitates the management of the composition ratio of the dicarboxylic acid and glycol of the slurry, which is an important process management item in slurry preparation, leading to the advantage that the control system for the management can be simplified. . In the case of this method, since the composition ratio of the dicarboxylic acid and the glycol can be adjusted in the slurry storage tank, there is an advantage that the composition ratio can be suppressed. In this method, slurry preparation may be carried out by a continuous method or a semibatch method. Moreover, you may implement combining this method and the former method.

  The set value of the slurry temperature is not limited, but is preferably from room temperature to 180 ° C. In the present invention, as described later, it is preferable that the recovered glycol recovered by the implant is recycled and reused. The recovered glycol is preferably circulated in a heated state from the viewpoint of energy efficiency. Therefore, since the recovered glycol is in a warmed state, the set temperature is preferably a warmed state, and more preferably 70 to 150 ° C. In the present invention, the temperature variation of the recovered glycol that is recycled and reused affects the slurry temperature variation. Therefore, temperature management and supply amount management of the recovered glycol are important management items.

  In the present invention, it is preferable to control the esterification reactor pressure to be within a set value ± 4%. Within ± 3% is more preferable. Within ± 2% is more preferable. On the other hand, the lower limit is most preferably ± 0% with no variation, but from the viewpoint of cost performance, ± 0.2% is preferable, and ± 0.5% is more preferable. When the esterification reaction tank pressure exceeds the set value ± 4%, it is not preferable because the variation of the carboxyl end group concentration of the oligomer at the outlet of the esterification reaction tank may exceed the range described later even if the control is performed. .

  The set value of the esterification reaction tank pressure is not limited, but is preferably from atmospheric pressure to 300 kPa as described above. 20-280 kPa is preferable, 40-260 kPa is more preferable, and it is preferable to adjust by the tower top pressure adjustment method of the distillation column which performs fractional distillation of the distilled glycol as mentioned later.

  Moreover, since the molar ratio of dicarboxylic acid and glycol in the slurry also affects the esterification reaction, it is preferably controlled within a certain range. As the variation range, the range of the known technique described above is sufficient. A setting value within ± 0.3% is preferable. A set value within ± 0.25% is more preferable, and a set value within ± 0.2% is even more preferable. On the other hand, the lower limit is most preferably ± 0% which is unchanged, but from the viewpoint of cost performance, ± 0.01% is preferable, and ± 0.02% is more preferable.

  In the present invention, it is preferable that the carboxyl end group concentration of the oligomer at the outlet of the esterification reaction tank is within a set value ± 5%. Within ± 4% is more preferred, and within ± 3% is even more preferred. When the carboxyl end group concentration fluctuation exceeds ± 5%, the fluctuation of the subsequent polycondensation reaction is increased, and the uniformity of the quality of the obtained polyester is lowered. On the other hand, the lower limit is most preferably ± 0% with no variation, but from the viewpoint of cost performance, ± 0.2% is preferable, and ± 0.5% is more preferable.

  The set value of the carboxyl end group concentration is not limited, but is preferably in the range of 150 to 900 eq / ton. The range of 170-800 eq / ton is more preferable, and the range of 190-700 eq / ton is more preferable. When the set value of the carboxyl end group concentration is less than 150 eq / ton, the polycondensation activity is lowered and the production of diethylene glycol in the polycondensation step is increased, which is not preferable. In particular, when a polycondensation catalyst system having a large influence of the carboxyl end group concentration of the polyester oligomer on the polycondensation reaction activity is used, the polycondensation catalyst activity is remarkably lowered, which is not preferable. On the other hand, when the set value of the carboxyl end group concentration exceeds 900 eq / ton, the subsequent polycondensation reaction proceeds unstably, and fluctuations in the degree of polymerization of the resulting polyester increase. Moreover, since the carboxyl terminal group density | concentration of polyester obtained becomes high and leads to stability reductions, such as a hydrolysis stability of polyester, it is unpreferable.

  The method of setting the polyester oligomer carboxyl end group concentration at the outlet of the esterification reaction tank within the above range is not limited. For example, production equipment factors such as the structure of the esterification reaction apparatus, composition ratio of dicarboxylic acid and glycol in the slurry supplied to the esterification reaction tank, esterification reaction temperature, esterification reaction pressure, esterification reaction time, etc. What is necessary is just to set reaction conditions etc. suitably. Moreover, you may adjust by adding water to an esterification reaction process.

  In the present invention, the final product (polymer) is preferably filtered and then chipped. For such filtration, a filter having an opening of about 3 to 20 μm is usually used.

  As described above, the polyester resin obtained by the method of the present invention is heated in a solid phase under reduced pressure or under an inert gas stream, and the polycondensation is further advanced, or the cyclic 3 amount contained in the polyester resin. There are no restrictions on taking measures such as removing oligomers such as body and by-products such as acetaldehyde. Further, for example, it is possible to incorporate a treatment such as purifying a polyester resin by an extraction method such as a supercritical pressure extraction method to remove impurities such as the by-products.

  In the polyester of the present invention, other arbitrary polycondensates, antistatic agents, antifoaming agents, dyeability improvers, dyes, pigments, matting agents, fluorescent whitening agents, stabilizers, antioxidants, etc. The additive may be contained. As antioxidants, aromatic amine-based and phenol-based antioxidants can be used, and as stabilizers, phosphoric acid and phosphate ester-based phosphorus-based, sulfur-based, amine-based stabilizers, etc. Can be used.

  These additives can be added at any stage of polycondensation or after polycondensation of the polyester or at the time of polyester molding, and which stage is suitable depends on the structure of the target polyester and the polyester obtained. What is necessary is just to select suitably according to required performance, respectively.

  The polyester of the present invention is optimized for the specific resistance of the polyester, so that when the electrostatic adhesion method is applied in the melt extrusion casting, it can increase the electrostatic adhesion force that closely adheres the melt extruded sheet to the chill roll. Since the maximum casting speed that can be cast can be increased while suppressing the occurrence of pinner bubbles, it can be suitably used as a raw material for films and sheets that include a melt extrusion molding process.

  When used for films, in order to improve handling properties such as slipperiness, rollability, and blocking resistance, it is possible to include inert particles such as inorganic particles, organic salt particles and crosslinked polymer particles in the film. I can do it. These particles may be either inorganic / organic or hydrophilic / hydrophobic surface-treated or non-surface-treated. For example, for the purpose of improving the dispersibility of the particles, the surface treatment may be used. It may be preferable to use the prepared particles.

  Inorganic particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, lithium fluoride, Examples include sodium calcium aluminum silicate, hydrophobic treated silica, inorganic treated silica, organic treated silica, glass powder, and silicon.

  Examples of the organic salt particles include terephthalate such as calcium oxalate, calcium, barium, zinc, manganese, and magnesium. Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers of divinylbenzene, styrene, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin may be used.

  A method for incorporating the inert particles in the polyester as the base film is not limited, but (a) the inert particles are dispersed in a slurry form in a diol which is a polyester component, A method of adding polyester to a polymerization reaction system, (b) a method of adding a water slurry of inert particles dispersed in a molten polyester resin by a vent type twin screw extruder in a melt extrusion step of a polyester film, (c) polyester Examples include a method of kneading a resin and inert particles in a molten state (d) a method of kneading a polyester resin and a master resin of inert particles in a molten state.

  In the case of the method of adding to the polymerization reaction system, it is preferable to add the diol slurry of inert particles to the reaction system having a low melt viscosity before the esterification reaction or transesterification reaction and before the start of the polycondensation reaction. In addition, when adjusting the diol slurry of inert particles, it is preferable to perform a physical dispersion treatment such as a high-pressure disperser, a bead mill, or ultrasonic dispersion. Furthermore, in order to stabilize the dispersion-treated slurry, it is preferable to use an appropriate chemical dispersion stabilization treatment according to the type of particles used.

  As the dispersion stabilization treatment, for example, in the case of inorganic oxide particles or crosslinked polymer particles having a carboxyl group on the particle surface, an alkali compound such as sodium hydroxide, potassium hydroxide or lithium hydroxide is added to the slurry. Further, reaggregation between particles can be suppressed by electrical repulsion. In the case of calcium carbonate particles, hydroxyapatite particles, etc., it is preferable to add sodium tripolyphosphate or potassium tripolyphosphate to the slurry.

  In addition, when adding the diol slurry of inert particles to the polyester polymerization reaction system, heat treatment of the slurry to near the boiling point of the diol can also be applied to heat shock (addition between the slurry and the polymerization reaction system). (Temperature difference) can be reduced, which is preferable in terms of dispersibility of particles.

  These additives can be added at the time of polymerization of the polyester or after polymerization, or at any stage after the formation of the polyester film. Which stage is suitable depends on the characteristics of the compound and the required performance of the polyester film. It depends on each.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples. In addition, the evaluation method was implemented with the following method.

In the following Examples and Comparative Examples, TPA means terephthalic acid, EG means ethylene glycol, and TEPA means triethyl phosphate. Each characteristic and physical property value were measured by the following test methods.

(1) Intrinsic viscosity The polyester is dissolved in a mixed solvent of phenol (6 parts by weight) and 1,1,2,2-tetrachloroethane (4 parts by weight) and measured at 30 ° C.
(2) Polyester melt specific resistance (ρi)
Two electrode plates are placed in polyester melted at 275 ° C., a current value (i ₀ ) when a voltage of 120 V is applied is measured, and a specific resistance value ρi is obtained by the following equation.
ρi (Ω · cm) = A / l × V / i ₀
Here, A = electrode area (cm ² ), l = interelectrode distance (cm), and V = voltage (V).
(3) Amount of insoluble alkaline earth metal 100 g of polyester chip was washed with water and dried, and then dissolved in a 75:25 (weight ratio) mixed solvent of parachlorophenol and tetrachloroethane. The mixture was filtered through a membrane filter made of ethylene having an average pore diameter of 0.1 μm (PTFE membrane filter manufactured by Advantec, product name: T010A047A), and after drying the filter, the amount of alkaline earth metal in the residue on the filter was measured with fluorescent X-rays. This was converted into an amount per kg of polyester and displayed.
(4) Number of coarse particles in polyester (number of particles having a particle size of 5 μm or more)
A polyester chip (one grain) was sandwiched between two cover glasses, melt-pressed at 280 ° C., rapidly cooled, and observed with 20 fields of view with a 100 × phase contrast microscope, and the number of particles having a maximum diameter of 5 μm or more was counted. . Displayed in number per 2.4 mm ² .
(5) Electrostatic adhesion of polyester Obtained by providing a tungsten wire electrode between the die part of the extruder and the cooling drum, and casting by applying a voltage of 10 to 15 KV between the electrode and the casting drum. The surface of the casting is observed with the naked eye, and the casting speed is evaluated at the casting speed at which pinna bubble generation starts. The higher the casting speed, the better the electrostatic adhesion.
Example 1
Continuous polyester production comprising one continuous esterification reaction tank and two polycondensation reaction tanks, and an inline mixer with a high-speed stirrer installed in the transfer line from the esterification reaction tank to the polycondensation reaction tank The apparatus produces 1.1 parts by mass of ethylene glycol and 1 part by mass of antimony trioxide with respect to 1 part by mass of high-purity terephthalic acid. Prepared. The slurry was continuously supplied to the esterification reaction tank. A polyester oligomer was obtained at an esterification tank reaction temperature of 260 ° C. and a pressure of 180 kPa. In the esterification reaction step, the amount of heat per unit time of the reaction product staying in the esterification reaction tank is calculated from the temperature of the reaction product staying in the esterification reaction tank, the passing amount of the reaction product and the specific heat of the reaction product, The amount of heat per unit time of the slurry supplied to the esterification reaction tank was controlled so that the amount of heat was constant. The temperature of the reaction product staying in the reaction vessel was measured at a position 300 mm inside the can wall at the bottom of the reaction vessel. Moreover, the passing amount of the reactant in the esterification reaction tank was calculated from the amount of slurry supplied to the reaction tank and the liquid level of the esterification reaction tank. In addition, the slurry heat amount is adjusted by controlling the fluctuation of the slurry supply amount to be within ± 2.0% of the set value by changing the number of revolutions of the liquid feed pump using a rotary piston flow meter. Was done. The unit time for calorific value calculation was calculated per hour. In the slurry preparation, the high-purity terephthalic acid temperature supplied to the slurry preparation tank is measured in a measuring tank immediately before the supply port, and the high-purity terephthalic acid is brought in from the high-purity terephthalic acid temperature, its supply amount and specific heat. The amount of heat was determined and controlled by changing the glycol temperature supplied to the slurry preparation tank so that the slurry temperature in the slurry preparation tank was constant. The glycol temperature is set by calculating the amount of glycol heat supplied to the slurry preparation tank necessary for making the slurry temperature constant in the slurry preparation tank, and adding a temperature adjustment function to the slurry preparation tank. The method was carried out by increasing the temperature adjustment accuracy. The amount of heat fluctuation per unit time of the reactant staying in the esterification reaction tank was ± 0.8%. The slurry temperature supplied to the esterification reaction vessel was controlled in terms of calorie with 110 ° C. as the center value. Further, the fluctuation of the molar ratio of ethylene glycol and terephthalic acid was controlled within ± 0.25%. The molar ratio was adjusted by measuring the amount of terephthalic acid in the slurry using a near-infrared spectrophotometer and adjusting the amount of ethylene glycol supplied to the slurry preparation tank. The pressure fluctuation in the esterification reaction tank was controlled within ± 1.3%. Moreover, the fluctuation | variation of the liquid level of the esterification reaction tank was within ± 0.2%.

  An EG solution containing magnesium acetate in an amount of 60 ppm Mg atoms with respect to the generated PET and an EG solution containing TEPA in an amount of 40 ppm P atoms with respect to the generated PET were added to the agitated in-line mixer. . Moreover, sodium acetate of the quantity from which Na atom will be 3 ppm with respect to production | generation PET was added to the esterification reaction tank. The in-line mixer has a high-speed stirrer with a turbine-like mixer blade disposed in a mixer casing through a narrow gap, and has a rotational speed of 2500 rpm and a peripheral speed of 26.5 m / sec. Stir.

  The esterification reaction product is continuously transferred to a continuous polycondensation apparatus. The initial polymerization reactor is 265 ° C. and 0.009 MPa, the intermediate polymerization reactor is 270 ° C. and 0.0007 MPa, and the final polymerization reactor is 272. This was carried out at 0.0000133 MPa at 0 ° C. to obtain PET having an intrinsic viscosity of 0.620 dl / g. The quality fluctuations of the oligomer and polyester obtained in this example were small and stable. The results are shown in Table 1. In addition, the initial value of the clarity of polyester is evaluated about the polyester obtained when 5 days have passed since the manufacture of the polyester was started. The same treatment was applied to the following examples and comparative examples.

Further, the following formula (1) is obtained from the maximum value, the minimum value, and the average value of 50 samples of carboxyl end groups of the oligomers at the outlet of the esterification reaction vessel of 50 samples sampled every 12 hours (for 25 days). The obtained fluctuation range was small and the esterification reaction was stable.
[{(Maximum value−minimum value) × 1/2} / average value] × 100 (%) (1)
In addition, the carboxyl terminal group of the oligomer was evaluated by the following method.
[Oligomer carboxyl end group concentration]
The oligomer was pulverized by a handy mill (pulverizer) without exhibiting drying. A sample of 1.00 g was precisely weighed and 20 ml of pyridine was added. Several grains of zeolite were added and dissolved by boiling for 15 minutes. Immediately after boiling and refluxing, 10 ml of pure water was added and allowed to cool to room temperature. Titration with N / 10-NaOH was performed using phenolphthalein as an indicator. Do the same for the blank without the sample. When the oligomer did not dissolve in pyridine, the reaction was carried out in benzyl alcohol. AVo (eq / ton) is calculated according to the following equation.
AVo = (A−B) × 0.1 × f × 1000 / W
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))
The quantitative value was measured three times and the average value was used.

  The polyester obtained in this example was excellent in electrostatic adhesion, high in clarity and high quality. Moreover, the high clarity was maintained over a long period of time, and it was shown that high-quality polyester can be produced stably and continuously over a long period of time.

Example 2
In the method of Example 1, the supply of the EG solution containing TEPA is divided into two parts, an esterification reaction tank and an in-line mixer, and added so that P atoms become 10 ppm and 30 ppm with respect to the generated PET, respectively. A polyester was obtained in the same manner as in Example 1 except for changing to. The results are shown in Table 1.

  The polyester obtained in this example had high clarity and high quality. Moreover, the high clarity was maintained for a long time, and it was shown that high quality polyester can be produced stably. Furthermore, the electrostatic adhesion was superior to the polyester obtained in Example 1.

Example 3
In the method of Example 2, a slurry storage tank having a stirrer and a temperature adjustment function is provided in the middle of the transfer line from the slurry preparation tank to the esterification reaction tank, and the slurry temperature is controlled also in the slurry storage tank. A polyester was obtained in the same manner as in Example 1, except that the temperature adjustment accuracy was changed. The variation in the amount of heat per unit time of the reactant staying in the esterification reaction tank was improved to ± 0.4%. The results are shown in Table 1.
The variation in the carboxyl end group concentration of the polyester oligomer in this example was further suppressed than in the methods of Example 1 and Example 2.

Reference example 4
In the method of Example 1, polyester was obtained in the same manner as in Example 1 except that the control of the amount of heat per unit time of the reaction product remaining in the esterification reaction tank and the control of the slurry temperature were canceled. . The amount of heat fluctuation per unit time of the reaction product staying in the esterification reaction tank was ± 4.9%. The results are shown in Table 1.
Also in this reference example, the clarity and electrostatic adhesion of the polyester were good as in Example 1, but the variation in the carboxyl end group concentration of the polyester oligomer was large.

Comparative Example 1
In the method of Example 1, the polyester of Comparative Example 1 was obtained in the same manner as in Example 1 except that the EG solution of magnesium acetate and TEPA was changed to being added to the esterification reactor without using an in-line mixer. It was. The results are shown in Table 1. The polyester obtained in this comparative example had good electrostatic adhesion and initial clarity, but a decrease in clarity was observed in long-term continuous production.

Comparative Example 2
Implementation was carried out except that the in-line mixer having the high-speed stirrer of Example 1 was changed to a static mixer, and the EG solution of magnesium acetate and TEPA was added so as to be added immediately before the static mixer from separate addition ports. A polyester was obtained in the same manner as in Example 1. The results are shown in Table 1. The polyester obtained in this Comparative Example had the same problems as the polyester obtained in Comparative Example 1.

Example 5
In the method of Example 1, an inline mixer having a high-speed stirrer was installed in the transfer line from the slurry preparation tank to the esterification reaction tank, and the amount of Mg atoms in the inline mixer was 60 ppm with respect to the generated PET. A polyester was obtained in the same manner as in Example 1 except that an EG solution containing magnesium acetate and an EG solution containing TEPA in an amount of 40 ppm of P atoms were added to the produced PET. The results are shown in Table 1. The polyester obtained in this example was of high quality, although the clarity of the polyester was slightly lowered as compared with the polyester obtained in Example 1.

Example 6
In the method of Example 1, an in-line mixer having a high-speed stirrer is installed in a circulation line provided in the slurry preparation tank, and the in-line mixer contains magnesium acetate in an amount of 60 ppm of Mg atoms with respect to the generated PET. A polyester was obtained in the same manner as in Example 1 except that the EG solution and an EG solution containing TEPA in an amount of 40 ppm of P atoms were added to the produced PET. The results are shown in Table 1. The polyester obtained in this example was of high quality, although the clarity of the polyester was slightly lowered as compared with the polyester obtained in Example 1.

Example 7
In the method of Example 3, the transfer line from the esterification reaction tank to the polycondensation reaction tank is branched into two, and a flow path switching mechanism is provided so that the reaction product can flow through any of the lines, and Stirring in-line mixers were installed on both lines. An EG solution containing magnesium acetate in an amount of 60 ppm of Mg atoms with respect to the produced PET and an EG containing TEPA in an amount of 30 ppm of P atoms with respect to the produced PET. The solution was added and polyester production was started. After 8.5 months from the start of the production of the polyester, the amount of insoluble magnesium evaluated by the insoluble content evaluation method began to exceed 1 mg. Therefore, the flow line of the transfer line from the esterification reaction tank to the polycondensation reaction tank was switched, and the addition location of the magnesium acetate and TEPAEG solution was changed to an in-line mixer with a new flow path to continue production.

  The polyester obtained in this example was excellent in electrostatic adhesion similar to the polyester obtained in Example 3. In addition, a few extraordinary products were produced when the flow path was switched, but the polyester obtained even after one year of continuous production maintained a high degree of clarity, and high-quality polyester was stable over a long period of time. It has been shown that continuous production is possible.

According to the polyester production method of the present invention, a polyester having a good electrostatic adhesion and having a very high degree of clarification can be stably produced over a long period of time with little increase in the content of foreign matter even after operation. . Therefore, the polyester obtained by the production method of the present invention suppresses molding problems such as breakage, yarn breakage, and generation of eyes when forming into a film or fiber. Moreover, since it has extremely high clarity, it can be suitably used as a raw material for optical films, hollow molded articles, ultrafine denier fibers and the like that are required to have few foreign matters and defects. Therefore, it is important to contribute to the industry.

Claims (7)

In a method for producing a polyester comprising at least an alkaline earth metal compound and a phosphorus compound, a slurry comprising dicarboxylic acid and glycol prepared in a slurry preparation tank is continuously supplied to an esterification reaction tank, and one esterification is performed. perform an esterification reaction using a reaction vessel, subsequently a method for continuously producing by performing polycondensation in a polycondensation reaction tank, meets the following requirements at the same time, and retained in the esterification reaction tank The amount of heat per unit time of the reactant to be controlled is controlled to be within ± 1.5% of the set value calculated from the temperature of the reactant staying in the esterification reaction tank, the amount of reactant passed and the specific heat of the reactant. A process for producing polyester, characterized in that:
(1) The phosphorus compound is added to at least one location selected from the group consisting of a slurry preparation tank, an esterification reaction tank, a polycondensation reaction tank, and a transfer line between these tanks. (2) The alkaline earth metal Install a stirring-type inline mixer in at least one location selected from the group consisting of a slurry preparation tank, a transfer line from the slurry preparation tank to the esterification reaction tank, and a transfer line from the esterification reaction tank to the polycondensation reaction tank. And adding to the in-line mixer The method for producing a polyester according to claim 1, wherein the place where the alkaline earth metal compound is added is an in-line mixer installed in a transfer line from the esterification reaction tank to the polycondensation reaction tank. The method for producing a polyester according to claim 1 or 2, wherein the peripheral speed of the outer periphery of the stirring blade of the stirrer of the in-line mixer is 2 to 100 m / sec. 4. The method for producing a polyester according to claim 1, wherein a part of the phosphorus compound is added to an in-line mixer to which the alkaline earth metal compound is added. Measure the reactant temperature, slurry temperature, and slurry flow rate in the esterification reaction tank, and supply to the esterification reaction tank so that the amount of heat per unit time of the reactant remaining in the esterification reaction tank is within the above range. The method for producing a polyester according to claim 1, wherein the amount of heat per unit time of the slurry is controlled. At least from the start of the production of the polyester, the amount of alkaline earth metal in the residue on the filter after dissolving the obtained polyester in a solvent and filtering the solution with a membrane filter having an average pore size of 0.1 μm is 1 mg or less per kg of the polyester. It maintains over 3 months, The manufacturing method of the polyester in any one of Claims 1-5 characterized by the above-mentioned. Method for producing a polyester according to any one of claims 1 to 6, melt specific resistance at 275 ° C. of the resulting polyester is equal to or less than 0.5 × 10 ⁸ Ω · cm.